1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Statics-Two wires holding traffic light

  1. Nov 19, 2011 #1

    lrp3395

    User Avatar

    Screen Shot 2011-11-19 at 8.48.14 PM.png

    I dont know what i did wrong

    Find the tension in the two wires supporting the traffic light
    Mass of light= 33 kg
    θ of FT1= 53°
    θ of FT2=37°

    Ʃfx=0
    Ft1cos53-ft2cos37=0
    ft1cos53=ft2cos37

    Ʃfy=mg
    ft1sin53-ft2sin37=mg
    ft1sin53=mg+ft2sin37
    ft1=(ft2sin37+mg)/sin53
    ft1=1.33ft2

    1.33ft2=(ft2sin37+mg)/sin53
    1.33ft2=.72ft2+mg
    .61ft2=323.73 N
    Ft2=530.7n

    ft1cos53=ft2cos37
    ft1cos53=423.84n
    ft1=704.26n
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
    lrp3395, Nov 19, 2011
  2. jcsd
    Phys.org - latest science and technology news stories on Phys.org
  3. Nov 19, 2011 #2

    PhanthomJay

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Tension forces always pull away from the objects on which they act. In the horizontal direction, your equation is correct. Not so in the vertical direction.
     
    PhanthomJay, Nov 19, 2011
  4. Dec 8, 2012 #3

    ssnapier

    User Avatar

    This is what I got:
    TLsin(53o) + TRsin(37o) - 294 N= 0 TRcos(37o) - TLcos(53o) = 0
    TR = TLcos(53o)/cos(37o)

    TLsin(53o) + TRsin(37o) - 294N= 0
    TLsin(53o) + {TLcos(53o)/cos(37o)}sin(37o) - 294 = 0
    TLsin(53o) + TLcos(53o)tan(37o) = 294N
    TL(sin(53o) + cos(53o)tan(37o)) = 294N
    TL = (294 N)/(sin(53o) + cos(53o)tan(37o)) = 234.79884N = 230N

    TR = TLcos(53o)/cos(37o)
    TR = (234.79884 N)cos(53o)/cos(37o) = 176.9336 N = 180N

    Left wire has 230N of tension
    Right wire has 180N of tension
     
    ssnapier, Dec 8, 2012
  5. Dec 8, 2012 #4

    DeShark

    User Avatar

    I don't know where you got the 294N from? 33kg * 9.8 = 323N. g is 9.8, not 8.9!

    Your maths seems right though.

    You can check your answer easily also. 230sin(53) + 180sin(37) = 292N, which is close enough (since you rounded your answers) to 294.
     
    DeShark, Dec 8, 2012
  6. Dec 8, 2012 #5

    ssnapier

    User Avatar

    Well dangit... I guess I got that one wrong then!
     
    ssnapier, Dec 8, 2012
  7. Dec 8, 2012 #6

    Bill Nye Tho

    User Avatar

    PhantomJay is correct

    jzCpx.jpg

    Hope this helps.
     
    Bill Nye Tho, Dec 8, 2012
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Statics-Two wires holding traffic light

  1. Traffic light problem (Replies: 2)

  2. Building A Traffic Light (Replies: 3)

  3. A two-side 'A' shaped ladder and then tension in the wire that holds it together (Replies: 3)

  4. Steel wire holding fish (Replies: 1)

  5. Torques and a Traffic Light (Replies: 3)

Loading...